From an evolutionary perspective, how did our species evolve to have derp sleep for long hours? I understand that sleeping conserves energy, but it would also make humans vulnerable to predators and not getting killed should take priority over saving energy
In: Biology
The communal nature of humans meant we could get away with sleeping longer.
Some more recent discoveries suggest that your circadian rhythm is actually partially embedded in your genes, and the primary theory to why is from our early days; some people in a community would go to sleep and wake up earlier while others later. This meant that a community could always have at least a couple people awake at any given hour to alert the rest should a threat come about.
Additionally, early humans; even running into the early modern era; didn’t actually sleep the full 8 hours that we do today, instead having what was called “first sleep” and “second sleep.” Essentially, they would sleep for about 4 hours, wake up for a few hours, then sleep for another 4 hours. Among other things, this biphasic pattern would help to ensure that rule of “someone should be awake at all times.” Biphasic sleep was likey only abandoned during the Industrial Revolution, as artificial lighting and scheduled shift-work led to humans either having to go to bed later or getting up earlier, squeezing the two 4 hour blocks of sleep into the one 8 hour block we have today. What’s weird about it is, despite it disappearing just 200 years ago, we had completely forgotten about it until very recently, and even now there’s some loose interpretations as to how it actually worked.
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